Polyester resins are produced by means of an esterification reaction and/or a transesterification reaction of a polybasic acid and a polyhydric alcohol, in the presence of an animal or vegetable oil fatty acid, or an animal or vegetable oil, if necessary, and are widely employed for various uses such as a paint and the like.
Hitherto, known examples of a polyhydric alcohol for preparing a polyester resin include dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, neopentylglycol, and the like; trihydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, and the like; and tetrahydric alcohols such as pentaerytritol, and the like.
A paint film formed of a polyester resin which starting material components include the aforementioned polyhydric alcohol possesses a problem with regard to their resistance to both hydrolysis and alkali, which in turn limits their use.
In addition, EP545108A discloses an alkyd resin consisting of a polyester comprising a diol which possesses an alkyl group having two or more carbon atoms in a side chain, and a melamine resin. However, the aforementioned publication does not include a concrete disclosure of a composition consisting of a polyester comprising 2,4-dialkyl-1,5-pentanediol, and a melamine resin.
Additionally, in the case of using a conventional polyester resin composition derived from a polyhydric alcohol as a paint, a defect in the paint film, caused by contaminants which exist in the painting environment, i.e., cissing tends to occur, and thus results in problems with the finish.